EVALUATION OF ELECTROCOAGULATION FOR CHLORIDE AND AMMONIUM REMOVAL FROM THE REJECT BRINE EFFLUENT PRETREATED BY SOLVAY PROCESS

Excessive use of desalination, due to the increase in freshwater demand, results in large productions of reject brine. Therefore, the development of an efficient treatment process of the reject brine becomes vital. The Solvay process is one of the main treatment technologies, wherein NH3 is introduced to convert soluble Na+ into insoluble NaHCO3. However, in this process, Cl- is not removed and NH4+ is introduced, and therefore electrocoagulation has been proposed for their removal. The experiment was designed using Minitab with different initial concentrations of chloride (7400 – 32600 mg/l), current densities (0.033 - 0.2 A/cm2), and temperatures (3.2 - 36.8°C). It was found that both percentage and rate of removal increased with the increase in temperature and current density, and the decrease in initial concentration of the ions. For example, at 20°C and initial concentrations of 14250 mg/l and 20000 mg/l for NH4+ and Cl-, respectively, increasing the current density from 0 to 0.2 A/cm2 resulted in an increase in the removal percentages from 12.5 to 66.7% and from 3.55 to 28.4% for NH4+ and Cl-, respectively. At 0.1167 A/cm2 and initial concentrations of 14250 mg/l and 20000 mg/l for NH4+ and Cl-, respectively, increasing the temperature from 3.2 to 36.8°C, resulted in an increase in the removal from 42.9 to 72.4% and from 21.8 to 29.8% for NH4+ and Cl-, respectively. However, at 0.1167 A/cm2 and 20°C, increasing the initial concentration of Cl- from 7400 to 32600 mg/l resulted in decreasing in the removal from 56.9 to 45.3% and from 30.3 to 25.6% for NH4+ and Cl-, respectively. The results were fitted into model equations (14 and 15), which were validated against an independent